In semiconductor manufacturing, semiconductor wafers often undergo many processing steps or stages before a completed die is formed. For example, such processing steps may include lithography, etching, semiconductor doping, and deposition and/or removal of various materials on the semiconductor wafer.
Time taken during different processing steps directly determines the throughput of the individual processes and final throughput of forming the completed die. Some processes, however, may require re-work on a workpiece, wherein corrections are made on the workpiece to attain various standards. For example, during chemical-mechanical polishing (CMP), one or more polishing steps may be performed at one or more respective polishing stations. Once the workpiece has passed through all of the polishing steps, various parameters are measured on the polished workpiece.
Conventionally, when one or more of the measured parameters are not within specifications after CMP processing, the workpiece is typically sent back into the same one or more polishing stations in order to achieve the desired parameters during what is called “re-work”. Such re-work techniques, however, typically decrease workpiece throughput through the CMP process, since the same polishing station is redundantly utilized for both the initial polish and the re-work polish. As workpiece sizes increase, such conventional re-work techniques using the same polishing stations decreases throughput due to the longer time taken to polish larger workpieces.